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Öğe Effects of natural hard shell particles on physical, chemical, mechanical and thermal properties of composites(SAGE Journals, 2021-05-31) Çelik, Yahya Hışman; Çelik, Kadir Serdar; Kılıçkap, ErolShelled herbal foods are widely consumed. The evaluation of the shells of these foods is important due to their features such as low cost, ease of recycling and environmental friendliness. In this study, hazelnut shell (HS), pistachio shell (PS), and apricot kernel shell (AKS) were brought to powder particles by grinding to dimensions of 300–425 µm. Some of the powder particles were converted into ash at 900°C. The amounts of cellulose, ash, humidity, and metal in these particles via chemical analyses were determined, while their structural properties via X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) analyses. Composite materials were produced by adding 15 wt.% to the polyester matrix material from these powder particles and ashes. Compression strength, hardness, specific weight, and thermal conductivity of these composites were analyzed. The lowest and highest humidity, ash, cellulose, hemicellulose, and lignin ratios in powders showed differences depending on the type of powders. The amount of Sn and K in the HS, PS, and AKS powders were close to each other, while the amount of Ca, Na, Mg, Fe, Mn, Cu, Zn and Si was higher in AKS powder. The reinforcement adding to the polyester increased the compression strength, hardness, specific weight and thermal conductivity properties.Öğe An artificial neural network model to predict the thermal properties of concrete using different neurons and activation functions(Hindawi, 2019-04-01) Fidan, Şehmus; Oktay, Hasan; Polat, Süleyman; Öztürk, SarperGrowing concerns on energy consumption of buildings by heating and cooling applications have led to a demand for improved insulating performances of building materials. The establishment of thermal property for a building structure is the key performance indicator for energy efficiency, whereas high accuracy and precision tests are required for its determination which increases time and experimental costs. The main scope of this study is to develop a model based on artificial neural network (ANN) in order to predict the thermal properties of concrete through its mechanical characteristics. Initially, different concrete samples were prepared, and their both mechanical and thermal properties were tested in accordance with ASTM and EN standards. Then, the Levenberg-Marquardt algorithm was used for training the neural network in the single hidden layer using 5, 10, 15, 20, and 25 neurons, respectively. For each thermal property, various activation functions such as tangent sigmoid functions and triangular basis functions were used to examine the best solution performance. Moreover, a cross-validation technique was used to ensure good generalization and to avoid overtraining. ANN results showed that the best overall R2 performances for the prediction of thermal conductivity, specific heat, and thermal diffusivity were obtained as 0.996, 0.983, and 0.995 for tansig activation functions with 25, 25, and 20 neurons, respectively. The performance results showed that there was a great consistency between the predicted and tested results, demonstrating the feasibility and practicability of the proposed ANN models for predicting the thermal property of a concrete.Öğe Characterization of hazelnut, pistachio, and apricot Kernel Shell particles and analysis of their composite properties(Taylor & Francis, 2021-05) Çelik, Yahya Hışman; Topkaya, Tolga; Kılıçkap, Erol; Başaran, Eyüp; Yalçın, RojinIn this study, hazelnut, pistachio, and apricot kernel shells were ground size of 0–300 µm, 300–600 µm, and 600–850 µm. The cellulose, ash, humidity, and metal contents of these powder particles were chemically analyzed and structural properties were characterized using X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectrometer (FT-IR) analysis. Their composites were fabricated by adding 0%, 10%, 20%, and 30% by weight of these powder particles to the polyester matrix material. The effect of chemical and structural properties of the powder particles on the physical, thermal, and mechanical properties of the composites was analyzed. The XRD analysis revealed that cellulose structure observed in powder particles. The peaks observed in their surface functional structures with FT-IR were mainly caused by cellulose and hemicellulose structures. These structures effected humidity and ash ratios. Nitrogen, carbon, hydrogen, and oxygen elements were seen in the structure. In addition, heavy metals such as Sn, Ca, K, Na, Mg, Fe, Ni, Mn, Cu, Zn, and Si were found. Powder particles added to the polyester material adversely affected the tensile strength of the matrix material. However, powder particles added to the matrix material at low rates had a positive effect on bending and compressive strength.Öğe Mechanical and thermophysical properties of lightweight aggregate concretes(Elsevier, 2015-10-15) Oktay, Hasan; Yumrutaş, Recep; Akpolat, AbdullahIn this study, experimental investigation is performed for producing new cement-based with relatively high strength, low density and good thermal properties for energy efficient buildings. Different types of concretes containing silica fume (SF), superplasticizer (SP) and air-entrained admixtures are prepared with a constant water–cement ratio, and normal aggregates replaced by lightweight aggregates (LWAs) including pumice (PA), expanded perlite (EPA) and rubber aggregates (RA) at different volume fractions of 10%, 20%, 30%, 40% and 50%. 102 samples with different materials and compositions are produced, and their characteristics are tested in accordance with ASTM and EN standards. Based on the experimental results, equations are presented to determine the relation between the thermophysical properties of composite samples. The investigation revealed that the addition of PA, EPA and RA reduced the material bulk density and compressive strength, and improved the insulation characteristics of the composite concretes. Furthermore, it was found out that the reductions in thermal conductivity and diffusivity of the produced samples reached to 82% and 74%, respectively.
